The present invention relates generally to the use of chitosan as an optical material, and more specifically to the use of chitosan and its derivatives as optical elements for electro-optic applications.
Holographic, diffractive and waveguiding optical elements have an important role in optical information processing, display and optical filtering applications. These applications require optically clear, low loss optical matrices.
A particularly important use for new optical elements is for optical limiters. Optical limiters are generally transparent optical elements that block, or limit to a maximum intensity, the transmission of incident light at specific wavelengths. A primary use for optical limiters will be for protection against laser radiation.
In recent years, substantial research has been conducted on using organic and polymeric materials as optical elements. While polymeric materials have exhibited relatively low optical loss at important communication wavelengths of 830 nm, 1.3 .mu.m and 1.5 .mu.m, favorable processing compatibility with microelectronic and optical devices and a wide variety of useful special properties such as refractive index tailoring, barriers still exist to producing successful new materials with combined needed attributes of, for example, low propagation loss, high temperature stability and excellent electronic packaging process capability.
Chitosan is a polysaccharide easily derived from chitin by N-deacetylation. Chitin is widely found in nature as a major component of the cell wall of various fungi and in the shells of insects and crustaceans. In recent decades, chitosan has received much attention for its special properties and inexpensive, abundant availability. Research has not only been concentrated in traditional areas such as waste water treatment and medical fibers and films, but also for potential applications in many other areas including industry, agriculture, food and biology. Contact lenses have been made from aminopolysaccharide compounds derived from chitosan.
Despite a need for new optical materials having new and improved properties suitable for use in newer optical elements, prior art investigation of organic and polymeric materials for new uses and research studying chitosan for a variety of new uses, have not included the possibility of using chitosan or a derivative as an optical element for a electro-optic application.
It is, therefore, a principal object of the present invention to provide optical elements made from chitosan and its derivatives for use in electro-optical applications.
It is another object of the present invention to provide optical waveguiding materials made from chitosan films.
It a further object of the present invention to provide chitosan gel systems as host materials for optical limiters.
It is a feature of the present invention that chitosan has a high affinity for dyes.
It is another feature of the present invention that chitosan has active amine groups which can be protonated to ammonium (NH.sub.3.sup.+) groups to create an inherent positive electrostatic charge.
It is a further feature of the chitosan that it has high optical clarity and exhibits low loss over a broad band of wavelengths.
It is still another feature of the present invention that chitosan has a high laser damage threshold.
It is a still further feature of the present invention that chitosan is stable to heat, light, moisture and many chemicals.
It is yet another feature of the present invention that chitosan has a high decomposition temperature.
It is a yet further feature of the present invention that chitosan has a high ability to absorb metal cations.
It is an advantage of the present invention that chitosan is widely and inexpensively available.
It is another advantage of the present invention that chitosan has excellent processability to form films, coating materials and fibers.
These and other objects, features and advantages of the present invention will become apparent as the description of certain representative embodiments proceeds.